yours looks like someone tried to loosen the alt with it, before loosening the rear three bolts/nut...
FIRST loosen the three 17mm bolts from the rear of the alternator.
then loosen the 13mm nut on the bracket bolt.
then pivot the thin threaded part up out of the way, and remove the belt from the alt, and let it dangle... don't worry, it can't go anywhere, the ps and a/c belts keep it on.
anyway, take a hammer and gently tap the fork part back flat so it almost touches the bracket again, and slide the 13mm nut groove into the fork.
then slide the alt out far enough to get the threaded rod into the nut, and put the belt back on. then tighten the nut slowly until the belt feels tight, then tighten the three bolts on the back, and you are done!

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!